Abstract:
Ternary complexes provide models for metalloenzymes and scveral other
biological processes involving metal ions. These have great functional values
in nature, such as in blood (hemoglobin) which is an iron-complex and
functions as thc oxygen carrier of the blood stream. The principles of
coordination chemistry will thus allow an increasing understanding of the
structure and dynamic features involved in biochemical processes.
Ternal)' metal complexes of type [MAL], where M=Cu(II), Ni(IT), & Zn(ll),
A=Ascorbic Acid (AsA), Pyridoxine (Pyri), Nicotinic Acid (Nia) and L=aalanine(
a-ala), Glycine(gly), Phenylalanine(ph-ala), and Tyrosine(tyro) havc
been investigated potentiometrically at 2SoC and at ionic strength of
O.2M(NaCI04). The stability constants have been detemlined using SCOGS
(Stability Constant of Gcneralized Species) compulcT program.
The stabilities in ternary complexes have been discussed in lernls of ligandligand
interaction, steric statistical, basicity of the ligands, nature of donor
sites and ellargc neutralization tactors. The stabilization is expressed in tenns
of L\logK. The L\logK values and percentage species computed gave parallel
evidence for the stabilization of ternary complexes. The stabilitics of ternary
complexes have been quantitatively compared with each other.
Ternary complexes containing Pyridoxine (Pyri) are found to be more stable
than the corresponding complexes containing Ascorbic Acid(AsA) and
Nicotinic acid(Nia). With respect to ligand L, the stability of ternmy
complexes increases in order: glycine < a-alanine < phcnylalanine <
tyrosine. Ternary complexes of Ni(JI) are found to be less stable than thc
corresponding Cu(lI) and Zn(lI) complexes.
The fOl1llalionof the complexes have been confinued by LN spectral sludies
and Cyelic Voltammogram.
